U.S. patent number 9,985,607 [Application Number 14/424,982] was granted by the patent office on 2018-05-29 for multiplexer having fewer intermodulation products.
This patent grant is currently assigned to SnapTrack, Inc.. The grantee listed for this patent is Snaptrack Inc.. Invention is credited to Gabriele Kolb, Andreas Link.
United States Patent |
9,985,607 |
Link , et al. |
May 29, 2018 |
Multiplexer having fewer intermodulation products
Abstract
A multiplexer (MUL) having fewer intermodulation products is
specified. For this purpose, the multiplexer (MUL) comprises a
transmit and/or receive filter (Tx, Rx), which operates with
acoustic waves, and blocker electrodes (EL1, EL2) for diverting
undesired frequency components to ground (GND). The blocker
electrodes (EL1, EL2) are arranged in this case on the same chip
(CH) as the filter which operates with acoustic waves.
Inventors: |
Link; Andreas (Laaber,
DE), Kolb; Gabriele (Munich, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Snaptrack Inc. |
San Diego |
CA |
US |
|
|
Assignee: |
SnapTrack, Inc. (San Diego,
CA)
|
Family
ID: |
48900992 |
Appl.
No.: |
14/424,982 |
Filed: |
July 30, 2013 |
PCT
Filed: |
July 30, 2013 |
PCT No.: |
PCT/EP2013/066014 |
371(c)(1),(2),(4) Date: |
February 27, 2015 |
PCT
Pub. No.: |
WO2014/032889 |
PCT
Pub. Date: |
March 06, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150236840 A1 |
Aug 20, 2015 |
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Foreign Application Priority Data
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Aug 30, 2012 [DE] |
|
|
10 2012 108 030 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03H
9/725 (20130101); H04L 5/14 (20130101); H04B
15/00 (20130101); H03H 9/706 (20130101) |
Current International
Class: |
H03H
9/70 (20060101); H04L 5/14 (20060101); H03H
9/72 (20060101); H04B 15/00 (20060101) |
Field of
Search: |
;333/133 ;455/78,83 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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1276245 |
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EP |
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1653615 |
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EP |
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1758247 |
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2001285123 |
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JP |
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JP |
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2011211347 |
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Oct 2011 |
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JP |
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2012147175 |
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Aug 2012 |
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JP |
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WO-2007000929 |
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Jan 2007 |
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WO |
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WO-2012020595 |
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Feb 2012 |
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WO |
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WO-2013061694 |
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May 2013 |
|
WO |
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Other References
Machine English Translation of Foreign Patent JP2011-193080 which
was Published on Sep. 29, 2011. cited by examiner .
Nishihara, T. et al.: "BAW/SAW/IPD hybrid type duplexer with Rx
balanced output for WCDMA Band I", Microwave Symposium Digest, 2008
IEEE MTT-S International, IEE, Piscataway, NJ, USA, Jun. 15, 2008,
pp. 831-834, ISBN: 978-1-4244-1780-3. cited by applicant .
International Search Report and Written
Opinion--PCT/EP2013/066014--ISA/EPO--dated Oct. 23, 2013. cited by
applicant.
|
Primary Examiner: Pascal; Robert J
Assistant Examiner: Salazar, Jr.; Jorge
Attorney, Agent or Firm: Patterson & Sheridan,
L.L.P.
Claims
What is claimed is:
1. A multiplexer (MUL) which operates with acoustic waves,
comprising: a transmit terminal (TxC), a receive terminal (RxC),
and a common terminal (CC); a transmit path, which is
interconnected between the transmit terminal (TxC) and the common
terminal (CC) and comprises a transmit filter (Tx); a receive path,
which is interconnected between the receive terminal (RxC) and the
common terminal (CC) and comprises a receive filter (Rx); a chip
(CH); and two or more blocker paths interconnected with the common
terminal (CC) and comprising blocker electrodes (EL1, EL2) arranged
on the chip (CH), which are provided to divert blocker signals to
ground (GND), wherein: at least one of the transmit filter (Tx) or
the receive filter (Rx) has a bulk acoustic wave (BAW) resonator;
the two or more blocker paths have at least one BAW resonator; and
at least one of the two or more blocker paths (BP) comprise one or
more stop circuits for blocker frequencies, wherein the one or more
stop circuits is interconnected between an antenna terminal and the
common terminal (CC).
2. The multiplexer (MUL) of claim 1, wherein at least one of the
two blocker paths (BP) comprise circuit elements of the transmit
filter (Tx) or the receive filter (Rx).
3. The multiplexer (MUL) of claim 1, wherein each of two or more
blocker paths or each of the at least one BAW resonator of the two
or more blocker paths diverts two blocker frequencies.
4. The multiplexer (MUL) of claim 1, further comprising: one or
more further transmit paths each having a further transmit filter
(Tx2, . . . , Txm); and one or more further receive paths each
having a further receive filter (Rx2, . . . , Rxn).
5. The multiplexer (MUL) of claim 1, wherein at least one of the
transmit filter (Tx) or the receive filter (Rx) operates with
surface acoustic waves, with bulk acoustic waves, or with guided
bulk acoustic waves.
6. The multiplexer (MUL) of claim 5, wherein the transmit filter
(Tx) comprises BAW resonators and the receive filter (Rx) comprises
SAW resonators, and wherein the BAW resonators and the SAW
resonators are arranged on or in various chips.
7. The multiplexer (MUL) of claim 1, wherein the chip (CH)
comprises all circuit elements of at least one of the transmit
filter (Tx) or the receive filter (Rx).
8. The multiplexer (MUL) of claim 1, wherein at least one of the
two or more blocker paths (BP) comprise an inductive element (IE),
which is embodied as a metallization in the transmit filter (Tx) or
in the receive filter (Rx) on the chip (CH), as a metallization in
a multilayer substrate, on which the chip (CH) is arranged, as a
discrete element on a module, which contains the chip (CH), or as a
discrete element on a circuit board, which is interconnected with
the chip (CH).
9. The multiplexer (MUL) of claim 8, wherein the inductive element
(IE) is a parasitic inductance of a feed line.
10. The multiplexer (MUL) of claim 1, wherein the at least one BAW
resonator of the two or more blocker paths has more or fewer layers
than one of resonators of at least one of the transmit filter (Tx)
or the receive filter (Rx).
11. The multiplexer (MUL) of claim 1, wherein one or more layers of
the at least one BAW resonator of the two or more blocker paths are
different in thickness from the BAW resonator of the at least one
of the transmit filter (Tx) or the receive filter (Rx).
12. The multiplexer (MUL) of claim 1, wherein a physical property
of a layer of the at least one BAW resonator of the two or more
block paths is different than physical properties of corresponding
layers of the BAW resonator of the at least one of the transmit
filter (Tx) or the receive filter (Rx).
13. The multiplexer (MUL) of claim 1, wherein a geometry of the at
least one BAW resonator of the two or more block paths is different
than a geometry of the BAW resonator of the at least one of the
transmit filter (Tx) or receive filter (Rx).
14. The multiplexer (MUL) of claim 1, wherein a first blocker path
of the two or more blocker paths (BP) is interconnected with a node
arranged between the transmit filter (Tx) and the common terminal
(CC), and a second blocker path of the two or more block paths is
interconnected with a node arranged between the receive filter (Rx)
and the common terminal (CC).
15. The multiplexer (MUL) of claim 1, comprising precisely one
transmit filter (Tx) and precisely one receive filter (Rx).
16. The multiplexer (MUL) of claim 1, wherein the transmit filter
or receive filter comprises band-pass filters or band-stop
filters.
17. The multiplexer (MUL) of claim 1, wherein at least one of the
two or more blocker paths (BP) comprises one or multiple stop
circuits for blocker frequencies, wherein the one stop circuit or
the multiple stop circuits are interconnected between the common
terminal (CC) and the receive filter or the transmit filter.
18. The multiplexer (MUL) of claim 1, the transmit path having a
band-stop filter, which is non-transmissive for blocker frequencies
in relation to the receive path.
19. The multiplexer (MUL) of claim 18, wherein the transmit filter
(Tx) is a bidirectional single filter.
20. The multiplexer (MUL) of claim 18, wherein the band-stop filter
is a bidirectional single filter.
21. The multiplexer (MUL) of claim 18, wherein the transmit filter
(Tx) or a further multiplexer follows the band-stop filter on a
side facing away from an antenna.
22. The multiplexer (MUL) of claim 1, wherein the multiplexer (MUL)
is contained in a mobile communication device having a further
filter or multiplexer and having two antennas.
23. The multiplexer (MUL) of claim 22, wherein the further filter
is a receive filter for GPS, Glonass, Galileo, or Compass
signals.
24. A mobile communication device comprising: a first multiplexer
and one or more second multiplexers, each of the first and one or
more second multiplexers according to claim 1; and two or more
antennas interconnected with the first and one or more second
multiplexers.
25. The mobile communication device of claim 24, wherein the first
multiplexer is configured to divert blocker signals from the one or
more second the multiplexers.
26. The multiplexer (MUL) of claim 1, wherein a first or second
order high-pass, a first or second order low-pass, a first or
second order band-pass, or a first or second order band-stop filter
is connected to at least one of the transmit or receive filter in
the transmit and receive paths.
27. The multiplexer (MUL) of claim 26, wherein the at least one
first or second order high-pass, a low-pass, a band-pass, or a
band-stop filter is constructed from capacitive and/or inductive
elements.
28. A multiplexer (MUL) which operates with acoustic waves,
comprising: a transmit terminal (TxC), a receive terminal (RxC),
and a common terminal (CC); a transmit path, which is
interconnected between the transmit terminal (TxC) and the common
terminal (CC) and comprises a transmit filter (Tx); a receive path,
which is interconnected between the receive terminal (RxC) and the
common terminal (CC) and comprises a receive filter (Rx); a chip
(CH); and a blocker path (BP), which is interconnected with the
common terminal (CC), wherein the blocker path (BP) comprises
blocker electrodes (EL1, EL2) arranged on the chip (CH), which are
provided to divert blocker signals to ground (GND), and wherein the
multiplexer (MUL) is contained in a mobile communication device
having a further filter or multiplexer and having two antennas, and
diverts blocker signals to ground, which are coupled from one
antenna into the other antenna.
Description
FIELD OF INVENTION
The invention relates to multiplexers having fewer intermodulation
products, in particular multiplexers in which frequency components
which can result in undesired intermodulation effects are
suppressed or eliminated.
BACKGROUND
Intermodulation products or intermodulation distortions (IMD) occur
in nonlinear systems and therefore in real technical systems when
two or more signals of different frequencies are processed. It can
thus occur that during mixing on a nonlinear circuit element,
products of the two signals are generated. In the case of two
signals of the form U.sub.1(t)=A.sub.1 cos(.omega..sub.1t) and
U.sub.2(t)=A.sub.2 cos(.omega..sub.2t) a plurality of frequency
components m.omega..sub.1+/-n.omega..sub.2 result with m, n=0, 1,
2, . . . , wherein the sum m+n specifies the order. If a resulting
frequency component is a multiple of a fundamental tone
.omega..sub.1 or .omega..sub.2, this is referred to as a harmonic.
If it is the total of multiples of the two fundamental tones, it is
referred to as an intermodulation product.
In multiplexers and especially in duplexers, those intermodulation
products are problematic which arise at an antenna input and are
located in the Rx band or in the vicinity of the Rx band. They
"block" the Rx signal path, since they cannot simply be filtered
out by filtering measures. Otherwise, the Rx useful frequency would
also be destroyed. Such undesired intermodulation products can
arise in particular in duplexers due to the multiplication of Tx
signals with a blocker signal received externally via the antenna.
The Rx passband associated with a Tx signal is relatively close,
usually above the Tx passband, in the case of a duplexer.
Therefore, harmonics of the Tx signal do not fall, but
intermodulation products of the Tx signal and an externally
received signal do fall in its own Rx passband.
In comparison to harmonics which can be removed by high-pass
filters or local poles in the stopband of a transmit filter, a way
other than filtering out must therefore be selected.
Providing BAW resonators, which are connected in antiparallel to
one another, to reduce nonlinear effects is known from DE 10 2005
028 927 A1.
This has the disadvantage that space on the surface of a costly
chip must be provided for the additional resonators.
SUMMARY OF INVENTION
It is therefore one object of the present invention to specify a
multiplexer having fewer intermodulation effects, which meets
current miniaturization requirements, does not restrict the power
compatibility, in which the slope of the filter flanks is not
reduced, and which is suitable for mass production. In particular,
it is an object of the present invention to specify a multiplexer,
in which blocker frequencies are already eliminated at antenna
nodes themselves or in the circuit region close to the antenna.
Furthermore, the multiplexer is to be produced cost-effectively and
is to have measures for reducing intermodulation effects, which may
be combined easily with measures for reducing intermodulation
effects because of other blocker frequencies. Furthermore, it is an
object to specify an improved multiplexer, in which no additional
manufacturing steps are necessary during the production and in
which additional external circuit elements are not absolutely
necessary. Furthermore, the multiplexer is to be compatible with
other measures for reducing intermodulation effects. Furthermore,
the electrical properties of the multiplexer are not to be worsened
by the measures for reducing the intermodulation effects.
These objects are achieved by a multiplexer as described herein.
Embodiments of the multiplexer as described herein provides
advantages over conventional devices
The invention comprises a multiplexer which operates with acoustic
waves, having a transmit terminal, a receive terminal, and a common
terminal. The multiplexer furthermore comprises a transmit path,
which is interconnected between the transmit terminal and the
common terminal and comprises a transmit filter, and a receive
path, which is connected between the receive terminal and the
common terminal and comprises a receive filter. Furthermore, the
multiplexer contains a chip and a blocker path, which is
interconnected with the common terminal. The blocker path comprises
blocker electrodes arranged on the chip in this case, which are
provided to divert blocker signals to ground. In this case, blocker
signals are those signals which, when multiplied with other signals
propagating in the multiplexer, result in intermodulation products,
which can lie in particular in an Rx frequency range and therefore
block the Rx path. Accordingly, blocker electrodes are those
electrodes which are designed accordingly to divert the blocker
signals to ground.
A multiplexer is thus specified, in which blocker signals are
diverted accordingly via suitable measures, so that mixing with
signals occurring regularly in multiplexers does not occur at all
in the ideal case and therefore intermodulation products are also
not generated.
The multiplexer operates with acoustic waves. For example, surface
acoustic waves (SAW), bulk acoustic waves (BAW), or guided bulk
acoustic waves (GBAW) come into consideration. In each of these
cases, electrode structures are used in conjunction with a
piezoelectric material for conversion, because of the piezoelectric
effect, between acoustic vibrations and electrical high-frequency
signals. Multiplexers operating with acoustic waves thus have
electrodes, which are arranged in the form of structured electrode
fingers on a piezoelectric substrate (in the case of surface
acoustic waves or guided surface acoustic waves) or which enclose a
piezoelectric layer like a sandwich and are implemented in a large
area. In the case of surface acoustic waves or guided surface
acoustic waves, the chip comprises the piezoelectric material in
this case. In the case of bulk acoustic waves, the sandwich
structure made of electrodes and piezoelectric material is
arranged, possibly together with mirror layers, on a carrier chip.
The provision of blocker electrodes to divert blocker signals to
ground is therefore compatible with conventional production
processes for multiplexers operating with acoustic waves.
Therefore, the blocker electrodes may easily be combined with the
circuit elements of the multiplexers and the object of the
invention is achieved in a simple but effective manner.
The term multiplexer relates in this case to a crossover having at
least one common terminal, which can be an antenna terminal, and a
number of m Tx signal paths and n Rx signal paths, wherein m and n
are natural numbers .gtoreq.1. In particular, it is possible that
the multiplexer is a duplexer having a Tx path and an Rx path.
The blocker electrodes can be electrodes of an acoustically active
filter element. An active blocker element can thus, solely by way
of its electrical effect, for example, as a capacitive element,
suppress or reduce blocker signals in a first frequency range and,
by way of its electroacoustic effect, suppress or reduce blocker
signals in a second frequency range, which is different from the
first frequency range. It is also possible that the blocker element
is designed so that its solely electrical effect and its
electroacoustic effect work together and suppress blocker signals
of a single frequency range still better.
In one embodiment, the blocker path comprises circuit elements of
the transmit filter or the receive filter.
In particular interdigital structures in the form of interdigital
converters or BAW resonators, which are constructed like
sandwiches, come into consideration as the circuit elements of the
transmit filter or the receive filter, which simultaneously
comprise blocker electrodes of the blocker path. Because these
structures are designed accordingly, they can simultaneously be
used as elements of the transmit path or the receive path, on the
one hand, and can represent circuit elements, via which blocker
signals can be diverted to ground, on the other hand.
In one embodiment, the multiplexer comprises one or more
resonators, which operate with acoustic waves, having blocker
electrodes in one or more blocker paths, wherein each blocker path
or each resonator, which operates with acoustic waves, having
blocker electrodes is provided to divert two blocker
frequencies.
In one embodiment, the multiplexer comprises one or more further
transmit paths each having a further transmit filter and one or
more receive paths each having a further receive filter. Thus, in
addition to a duplexer, triplexers, quadruplexers, etc. can also be
obtained easily.
In one embodiment, the transmit filter and/or the receive filter
operates with surface acoustic waves, with bulk acoustic waves, or
with guided bulk acoustic waves.
It is also possible that the transmit filter operates with one of
the specified types of acoustic waves, while the receive filter
operates with another type of acoustic waves. It is then possible
that the transmit filter or the electrode structures of the
transmit filter are arranged on a first chip and the receive filter
or the receive filter electrodes are arranged on a further chip.
The blocker electrodes can be arranged in this case on the first
chip and/or on the further chip. It is also possible that some
circuit elements of the blocker path are arranged on one chip,
while other circuit elements of the blocker path are arranged on
the further chip. The circuit elements of the blocker path can also
operate in this case with different types of acoustic waves.
In one embodiment, the transmit filter comprises BAW resonators and
the receive filter comprises SAW resonators. The BAW resonators and
the SAW resonators are arranged on or in various chips. Therefore,
a multiple die multiplexer is obtained, in which the different
filter technologies ensure the different requirements for transmit
and receive filters, for example, with regard to the power-handling
capacity, selection, insulation, etc.
In one embodiment, however, the chip comprises all circuit elements
of the transmit filter and/or the receive filter. The multiplexer
then operates with only one type of acoustic waves, wherein then
the circuit elements of the blocker path can also be arranged on
the chip.
In one embodiment, the blocker path comprises an electroacoustic
resonator, which is arranged on the chip.
The electroacoustic resonator of the blocker path can be in this
case a series or parallel branch resonator of the transmit filter
or the receive filter. The blocker path can comprise two or more
electroacoustic resonators. The blocker path can thus comprise, for
example, a series circuit of a resonator in the series branch,
followed by a further parallel branch.
Transmit or receive filters can comprise series and parallel branch
resonators interconnected in a ladder-type structure, wherein the
ladder-type structure represents a band-pass filter as a whole.
Only a part of the respective filter can also be embodied as a
ladder-type structure, while remaining filter elements comprise
alternative topologies, for example, DMS (dual-mode SAW)
structures.
The use of a parallel branch resonator, a transmit filter, or a
receive filter as a circuit element which comprises blocker
electrodes of the blocker path suggests itself in this case, since
parallel branch resonators, for example, in ladder-type circuits,
interconnect the signal path with ground. A ground path is thus
provided which interconnects the common terminal with ground and
via which blocker signals can be diverted to ground.
In one embodiment, the blocker path comprises an inductive element,
which is embodied as a metallization in the transmit filter or in
the receive filter on the chip.
It is also possible that the inductive element is embodied as a
metallization in a multilayer substrate, on which the chip is
arranged. Furthermore, it is possible that the inductive element is
embodied as a discrete element on a module, which contains the
chip, or as a discrete element on a circuit board, which is
interconnected with the chip.
Therefore, the blocker path comprises blocker electrodes which
represent a capacitive element and an inductive element. The
capacitive element and the inductive element can be interconnected
in series or in parallel and therefore can represent a resonant
circuit. The resonance frequency of the resonant circuit can be set
in this case so that its resonance frequency corresponds to the
frequency of blocker signals which are considered to be
particularly interfering.
Very generally, the capacitance of the capacitive element can be
set for this purpose by setting the area of BAW electrodes or the
aperture and the transducer length or the number of fingers of
interdigital structures. Furthermore, it is essentially also
possible to provide the spacing of the electrodes suitably to set
the capacitance.
The spacing of the electrode structures essentially determines the
wavelength of the acoustic waves, with which the multiplexer
operates. It is possible in this case that acoustically active
electrode structures are used as blocker electrodes in the blocker
path. However, it is also possible that electrode structures which
are acoustically inactive in the relevant frequency range are used.
The spacing and the area of the blocker electrodes can then be
selected essentially arbitrarily to set the capacitance of the
capacitive element.
The inductance of the inductive element can be set by the length of
the conductor sections of the inductive element. Furthermore, it is
possible to provide windings, wherein the number of windings can be
set to set the inductance of the inductive element. Overall, many
possibilities can thus be chosen to set the capacitance of the
capacitive element or the inductance of the inductive element, to
obtain good diversion of the blocker signals to ground.
In one embodiment, the inductive element has a low inductance. The
inductive element can thus be formed solely by a feed line, wherein
the inductance of the inductive element is then the parasitic
inductance of the feed line. If a low inductance is desired, the
inductance is thus obtained as an intrinsic inductance of a feed
line provided in any case, wherein space is saved and a multiplexer
component having a small structure is obtained.
In one embodiment, the transmit filter and/or the receive filter
has/have BAW resonators. The blocker path has a BAW resonator, the
mass coating of which deviates from the mass coating of the
resonators of the transmit filter and/or the mass coating of the
resonators of the receive filter.
A capacitive element is thus obtained in the blocker path, in which
the electrical and/or acoustic properties of the blocker electrodes
are optimized to divert blocker signals to ground. Furthermore, a
means is thus specified to advantageously set the acoustic
properties.
In one embodiment, the blocker path has a BAW resonator, which has
more or fewer layers than a resonator of the transmit filter or the
receive filter. The resonance frequency is thus strongly shifted
and an advantageous capacitive behavior is obtained in the
frequency range of the passbands.
In one embodiment, the blocker path (BP) has a BAW resonator (R),
in which one or more layers is/are different in thickness in
relation to a BAW resonator of the transmit filter (Tx) or receive
filter (Rx).
In one embodiment, the blocker path has a BAW resonator, wherein a
physical property of a layer is changed in comparison to the
physical properties of corresponding layers of resonators of the
transmit filter and/or receive filter. Changing physical
properties, for example, the mass coating, the thickness, the
number of the layers, the acoustic impedance, or the electrical
conductivity, represents a simple possibility for obtaining a BAW
resonator, which is not only part of the transmit filter and/or
receive filter, but rather is also part of the blocker path and
therefore must meet additional requirements.
In one embodiment, the blocker path comprises a BAW resonator, the
operating frequency of which is changed by changes in geometry in
comparison to BAW resonators of the transmit filter and/or receive
filter.
In addition to the above-mentioned properties, changes in geometry,
for example, a changed footprint of the resonator, can also be used
to obtain a resonator optimized toward multiple requirements.
A changed geometry in the case of multiplexers operating with
surface acoustic waves is possible, for example, by way of a
changed metallization height, a change of the pitch, i.e., a change
of the spacing of finger electrode center to finger electrode
center, or a change of the metallization ratio .eta..
The resonance behavior of a resonator is not arbitrarily
narrowband. Therefore, a positive effect is already achieved, even
if the resonance frequency of the resonant circuit--for example,
the blocker resonator alone or a series circuit of blocker
resonator and inductive element--is only in the vicinity of the
blocker band with regard to frequency. The resonance frequency of a
resonant circuit having a capacitance C and an inductance L is
at
.OMEGA. ##EQU00001## The inductance of the inductive element and
the capacitance of the capacitive element can be selected
accordingly, to divert blocker frequencies to ground.
In one embodiment, the blocker path comprises a capacitive element,
which is acoustically inactive. Such an acoustically inactive
element can be a capacitive element, which is only inactive in
corresponding frequency ranges, for example, Tx frequency range or
Rx frequency range, or which does not interact with acoustic waves
at all. For this purpose, it is possible, for example, to arrange a
non-piezoelectric material instead of a piezoelectric material
between BAW electrodes. It is also possible to use conductive
material from mirror layers of a BAW resonator, for example, from
the electrode material of the actual BAW electrodes, as the
electrodes for capacitive elements which are essentially
acoustically inactive. In addition, it is possible to interconnect
one of the actual BAW electrodes and a conductive mirror layer with
an intermediate layer of oxide to form a capacitive element.
In one embodiment, the multiplexer thus comprises a BAW resonator
having blocker electrodes, wherein at least one of the BAW
electrodes and/or a mirror layer comprising a conductive material
represents a blocker electrode.
Furthermore, it is possible, in the case of electrode structures
operating with surface acoustic waves or guided bulk acoustic
waves, to pivot the alignment of the finger electrodes in relation
to possible propagation directions of acoustic waves, so that the
electroacoustic coupling coefficient .kappa..sup.2 disappears. Such
capacitive elements solely have a capacitive effect, so that their
physical dimensions can be selected such that no negative
electroacoustic interaction occurs with Tx or Rx signals.
In one embodiment, the multiplexer comprises two or more blocker
paths having blocker electrodes arranged on the chip, which are
provided for diverting blocker signals to ground.
It is also possible to distribute various parts of one or more
blocker paths onto various chips, if the multiplexer comprises
multiple chips.
Thus, multiple blocker paths can be provided, wherein each blocker
path is provided for diverting a respective different blocker
signal to ground. Thus, a variety of blocker frequencies can be
made harmless, without intermodulation with Tx signals taking
place.
In one embodiment, the multiplexer comprises a transmit filter and
a receive filter. The multiplexer furthermore comprises a first
blocker path, which is interconnected with a node arranged between
the transmit filter and the common terminal, and a second blocker
path, which is interconnected with a node arranged between the
receive filter and the common terminal.
Furthermore, it is possible that a filter has two, three, four, or
more blocker paths.
Thus, intermodulations between various blocker frequencies and, on
the one hand, Tx signals from the transmit filter and, on the other
hand, signals which are reflected from the receive filter to the
common terminal or to the transmit filter, can be eliminated
easily.
In one embodiment, the multiplexer comprises precisely one transmit
filter and precisely one receive filter and thus represents a
duplexer.
If the total of the frequencies of the Tx signal and the blocker
signal essentially corresponds to the frequency of the Rx signals,
for example, in the WCDMA band 2 having Tx frequencies between 1880
MHz and 1910 MHz and Rx frequencies between 1930 MHz and 1990 MHz
at blocker frequencies around 20 MHz and 140 MHz, second-order
intermodulation products would lie in the Rx frequency range. In
such a situation, it is particularly advantageous if blocker
signals are eliminated in this simple manner so that
intermodulation products do not arise at all.
The diversion of blocker signals is accordingly also advantageous
if the absolute value of the difference of Tx signals and blocker
signals corresponds to the frequency of the Rx signals. This is the
case, for example, with blocker signals of the frequencies 3760 MHz
and 3900 MHz.
Furthermore, the situation, when the absolute value of the
difference of two times the Tx frequency and blocker frequency
corresponds to the Rx frequency, is of practical significance. This
is the case, for example, with blocker frequencies around 1770 MHz
and 1890 MHz and between 5630 MHz and 5810 MHz.
In one embodiment, resonators of the transmit filter and/or the
receive filter are embodied as doubled, wherein the resonators
which are doubled in each case are connected in antiparallel, to
reduce nonlinear effects.
In the case of the serial doubling, in this case one resonator is
replaced by two resonators connected one after another of doubled
area in each case, so that the total impedance of the doubled
resonators corresponds to the impedance of the replaced resonator.
In the case of parallel doubling, one resonator is replaced by two
resonators connected in parallel of half the area, to obtain the
same impedance of the replaced resonators. For this purpose, it is
possible with the aid of through contacts (vias) or bump
connections to interconnect an upper electrode of one resonator and
the lower electrode of the corresponding other resonator at a node
point.
In one embodiment, the common terminal is connected to ground via
an inductive element, so that an ESD protection is obtained. In
this case, the inductive element diverts ESD signals received
through the common terminal, for example, an antenna, directly to
ground, so that the transmit filter and in particular the sensitive
receive filter is protected from the broadband ESD signal.
It is also possible that the ESD protective path has, in addition
to the inductive element, a capacitive element connected in series
to the inductive element.
In one embodiment, the transmit path between the transmit filter
and the common terminal comprises an impedance adaptation network.
It is also possible that an impedance adaptation network is
arranged between the common terminal and the receive filter.
In one embodiment, the transmit filter of the multiplexer or the
receive filter of the multiplexer comprises a band-pass filter or a
band-stop filter. Band-pass filter and band-stop filter can both be
manufactured in SAW or BAW technology and therefore the
corresponding resonators can be arranged on the chip.
In one embodiment, the multiplexer comprises one or multiple stop
circuits for blocker frequencies, wherein the one stop circuit or
the multiple stop circuits are arranged between an antenna and the
common terminal CC.
In one embodiment, the multiplexer comprises a stop circuit between
the common terminal CC and a filter in the receive or transmit
path.
An acoustically active element can be interconnected in a stop
circuit.
In one embodiment, the multiplexer comprises a transmit path having
a band-stop filter, which is non-transmissive for blocker
frequencies in relation to a receive path. It is possible that the
transmit filter of the transmit path exclusively consists of the
band-stop filter. A band-stop filter can be a notch filter, for
example, the stop band of which is in the range of the receive band
of a receive path. The notch filter can comprise electroacoustic
resonators and inductive and/or capacitive circuit elements. Such a
notch filter is represented by a so-called extractor filter and is
suitable for interconnection with receive paths for
satellite-assisted systems such as GPS, Glonass, Compass, or
Galileo.
In one embodiment, the multiplexer is contained in a mobile
communication device having a further filter or multiplexer and
having two antennas. The multiplexer diverts blocker signals to
ground, which are coupled from one antenna into the other antenna.
Such a multiplexer is therefore suitable for mobile communication
devices having diversity functionality. A transmit signal of the
multiplexer can be coupled from an antenna interconnected with the
multiplexer into a further diversity antenna together with an
external blocker signal. This can result in undesired
intermodulation products in a further multiplexer, which is
interconnected with the further diversity antenna. To prevent this,
it is possible that the multiplexer or further multiplexers have
blocker paths, which divert the blocker signals in relation to
respective other multiplexers to ground. Such blocker paths can be
provided in the multiplexer or in further multiplexers.
In one embodiment, the mobile communication device comprises a
receive filter for GPS, Glonass, Galileo, or Compass signals as a
further filter.
In one embodiment, the further filter is a bidirectional single
filter, which can be provided, for example, for the fields of
application of Bluetooth or WLAN.
In one embodiment of the multiplexer, the multiplexer is
interconnected in a mobile communication device with a further
filter or multiplexer. The multiplexer is provided for diverting to
ground blocker signals, which would be coupled via an antenna
interconnected with the multiplexer into an antenna of the
communication device, which is interconnected with another signal
path. The multiplexer thus ensures that blocker signals which would
result in disturbances in other multiplexers are diverted to
ground.
In one embodiment, the multiplexer is interconnected in a mobile
communication device, wherein the mobile communication device
comprises a further filter or a further multiplexer. The
multiplexer is then provided to divert to ground blocker signals,
which would be coupled by crosstalk into another signal path of the
communication device. In addition to the above-mentioned
possibility that blocker signals can arrive via antennas in other
signal paths of a communication device without correspondingly
designed blocker paths, a possibility is now provided for
neutralizing blocker signals which would be coupled inside the
mobile communication device by crosstalk into other signal
paths.
In one embodiment of the multiplexer, the signal paths for
separation by high-pass, low-pass, band-pass, or band-stop filters
are interconnected with an antenna node.
In one embodiment, the multiplexer comprises a further filter,
which can be the above-mentioned further filter or a second further
filter. The further filter is a receive filter for GPS, Glonass,
Galileo, or Compass signals.
In one embodiment, the band-stop filter is a bidirectional single
filter.
In one embodiment, a further filter or a further multiplexer
follows the band-stop filter on the side facing away from the
antenna.
In one embodiment, the multiplexer is interconnected in a
communication device having one or more further multiplexers and
two or more associated antennas.
In one embodiment, the multiplexer diverts blocker signals from
outside and/or signals because of direct crosstalk between the
antennas from other multiplexers. In particular, those signals are
diverted which, if they were not diverted, would generate
interfering intermodulation products together or with its own
transmit signals.
In one embodiment, the multiplexer diverts blocker signals from
outside and/or signals because of direct crosstalk in its own
device, which can originate from other multiplexers of the device.
These signals would, if they were not diverted, generate
interfering intermodulation products together or with its own
transmit signals.
In one embodiment, the multiplexer comprises one or more blocker
paths for eliminating those intermodulation products which do not
interfere in its own multiplexer, but, if emitted via its own
antenna, could be coupled into one of the other antennas and could
cause interference therein in connected multiplexers.
In one embodiment, the multiplexer comprises one or more blocker
paths for eliminating intermodulation products, which do not
interfere in its own multiplexer, but would interfere due to direct
crosstalk in the device in other multiplexers.
In one embodiment, a lower-order high-pass, low-pass, band-pass, or
band-stop filter is connected upstream on the antenna side from at
least one transmit or receive filter in the transmit or receive
paths.
In one embodiment of this multiplexer, at least one or multiple or
all of the lower-order high-pass, low-pass, band-pass, or band-stop
filters is constructed from capacitive and/or inductive
elements.
In one embodiment, only the lower-order filter with one or more
blocker paths is contained in at least one signal path.
In one embodiment of the multiplexer, only the lower-order filter
with blocker paths is contained in at least one signal path.
In one embodiment, the multiplexer is a diplexer, triplexer,
quadplexer, or quintplexer, or a higher-value multiplexer.
The multiplexer will be explained in greater detail hereafter on
the basis of exemplary embodiments and schematic figures.
BRIEF DESCRIPTION OF THE DRAWINGS
In the figures:
FIG. 1A shows a chip surface having finger electrodes arranged
thereon of an interdigital transducer,
FIG. 1B shows a chip surface having a BAW resonator arranged
thereon,
FIG. 2A shows a multiplexer having a capacitive element in a
transmit filter,
FIG. 2B shows a multiplexer having a capacitive element in a
receive filter,
FIG. 2C shows a multiplexer, in which a common terminal is
connected to ground via a capacitive element,
FIG. 3 shows a multiplexer and typical signal paths of
intermodulation products,
FIG. 4 shows a multiplexer having a series resonant circuit in a
blocker path,
FIG. 5 shows a multiplexer having an electroacoustic resonator in a
blocker path,
FIG. 6 shows a multiplexer having an acoustic resonator and an
inductive element in a blocker path,
FIG. 7 shows a multiplexer having double-embodied resonators in a
transmit or receive filter,
FIG. 8 shows the equivalent circuit diagram of an acoustic
resonator,
FIG. 9 shows a multiplexer having a parallel branch resonator in
the blocker path of a transmit or receive filter,
FIG. 10 shows a multiplexer having a series branch resonator and a
parallel branch resonator in a transmit or receive filter,
FIG. 11 shows a multiplexer having two inductive elements and an
electroacoustic resonator in a blocker path,
FIG. 12 shows a multiplexer having two inductive elements and two
electroacoustic resonators in a blocker path,
FIG. 13 schematically shows an embodiment in which a transmit
filter is a notch filter,
FIG. 14 schematically shows the use of a multiplexer in a mobile
communication device having more than one antenna,
FIG. 15 shows an embodiment of a multiplexer, wherein a stop
circuit made of an inductance L and an on-chip capacitance X is
connected between an antenna terminal ANT and the common terminal
CC,
FIG. 16 shows an embodiment of a multiplexer having a stop circuit
between the common terminal CC and a filter in the transmit
path.
DETAILED DESCRIPTION
FIG. 1A shows the arrangement of interdigital structures on a chip
surface. Interdigital structures IDS, which comprise electrode
fingers EFI, of an SAW resonator SAWR are arranged on the surface
of the chip CH. These interdigital structures interconnect a common
terminal CC of a duplexer with ground GND. In this case, the SAW
resonator SAWR can be interconnected with a transmit-filter-side
signal path (Tx) or receive-side signal path (Rx) of the duplexer
or directly to the common terminal CC. The interdigital structure
IDS of the SAW resonator SAWR can be acoustically active or
acoustically inactive in the operating range of the duplexer in
this case. Independently of the acoustic activity, such an
interdigital structure represents a capacitive element, which can
divert blocker signals to ground in the blocker path, so that
intermodulation products mixed from blocker signals and Tx or Rx
signals propagating in the duplexer do not arise.
The duplexer can operate with surface acoustic waves. It then
comprises further SAW resonators and the interdigital structures
IDS of the blocker path may be arranged without great effort and
without additional work steps on the chip CH. The chip CH can be in
this case a piezoelectric crystal, for example, made of LiTaO.sub.3
(lithium tantalate) or LiNbO.sub.3 (lithium niobate).
FIG. 1B shows the arrangement of a BAW resonator BAWR as a part of
the blocker path and its arrangement on a surface of a chip CH.
Similarly to the circuit of FIG. 1A, the BAW resonator can be
interconnected directly with the common terminal CC or with a
transmit-side (Tx) or receive-side (Rx) section of a signal path.
The BAW resonator BAWR comprises a first, lower electrode EL1 and a
second, upper electrode EL2. An insulating layer PL, which can be a
piezoelectric layer and can comprise AlN (aluminum nitride) or ZnO
(zinc oxide), is arranged between the two electrodes. The
electrodes EL1 and EL2 represent in this case the blocker
electrodes, via which blocker signals can be diverted to ground. If
the multiplexer operates with bulk acoustic waves, corresponding
BAW resonators are thus arranged on the chip CH during the
production of the duplexer. The arrangement of a further BAW
resonator BAWR for the blocker path or the provision of a BAW
resonator of the transmit or receive filter, which simultaneously
comprises the blocker electrodes for the blocker path, does not
represent additional effort during the production of the
multiplexer in this case.
The layer stack of the BAW resonator BAWR can be acoustically
active or acoustically inactive. In each case, it represents a
capacitive element, via which blocker signals can be diverted to
ground.
FIG. 2A shows an embodiment of a multiplexer having a Tx filter Tx
and an Rx filter Rx, wherein the Tx filter Tx is arranged between a
Tx terminal TxC and a common terminal CC and the Rx filter Rx is
arranged between a receive terminal RxC and the common terminal CC.
A capacitive element CE, which comprises the blocker electrodes of
the blocker path, is arranged in the transmit filter Tx and can
divert blocker signals via ground to reduce or prevent
intermodulation products.
FIG. 2B shows an embodiment of a multiplexer, wherein a capacitive
element CE, which comprises the blocker electrodes, is arranged in
the receive filter Rx.
FIG. 2C shows an embodiment of a multiplexer, wherein a capacitive
element CE, which comprises the blocker electrodes of the blocker
path, is interconnected directly with the common terminal CC. The
capacitive element CE is neither part of the transmit filter Tx nor
of the receive filter Rx in this case. However, the capacitive
element CE can be arranged on the same chip as the transmit filter
Tx or the receive filter Rx.
FIG. 3 shows a multiplexer having m transmit signal paths Tx1, Tx2,
. . . , Txm and m transmit filters Tx1, Tx2, . . . , Txm and n
receive signal paths having n receive filters Rx1, Rx2, . . . ,
Rxn. The first, second, or mth transmit filter is arranged in this
case between the first, second, or mth transmit terminal, on the
one hand, and the common terminal CC, on the other hand. The first,
second, nth receive filter Rx1, Rx2, Rxn is accordingly arranged in
this case between the first, second, or nth receive terminal RxC1,
RxC2, RxCn, on the one hand, and the common terminal CC, on the
other hand. FRx1, FRx2, . . . , FRxn are in this case the receive
frequencies, FTx1, FTx2, . . . , FTxm are the transmit
frequencies.
It is shown as an example how transmit signals of the first
transmit signal path from the first transmit filter Tx1 are mixed
together with, inter alia, undesired but unavoidable blocker
signals of the frequency f.sub.blocker of the common terminal CC
and in this case frequency components arise for which the second
receive filter Rx2 is transmissive. Such intermodulation products
can pass the second receive filter Rx2 and would block the
functional capability of the second Rx filter in conventional
multiplexers. The transmissivity of the second receive filter Rx2
cannot be arbitrarily reduced here, since otherwise desired signals
to be received of the same frequency range also could not pass the
second receive filter Rx2.
The central idea of the invention is accordingly to divert blocker
signals of the frequency F.sub.blocker via the blocker path to
ground so that mixing with the transmit signals from the first
receive filter Tx1 is suppressed in the ideal case but at least
significantly attenuated.
Specifically, the second receive filter Rx2 can then maintain its
high transmissivity for the corresponding frequencies f.sub.Rx2,
whereby undisturbed reception of corresponding signals is
possible.
This is only one exemplary embodiment of a multiplexer. It is also
possible to obtain a multiplexer in which duplexers, triplexers,
etc. are embodied as cascaded.
FIG. 4 shows an embodiment of a multiplexer, wherein the blocker
path BP comprises a capacitive element CE and an inductive element
IE, which are connected in series. The blocker path is
interconnected directly with the common terminal CC in this case.
It is possible, but not absolutely necessary, that an adaptation
network MN is arranged between the transmit filter Tx and the
common terminal CC. It is furthermore possible, but not absolutely
necessary, that a further adaptation network MN is arranged between
the receive filter Rx and the common terminal CC. The capacitive
element CE of the blocker path BP comprises in this case the
blocker electrodes, which are arranged together with electrodes of
the resonators of the transmit filter or the receive filter.
The capacitive element CE can be an acoustically active element or
an acoustically inactive element in this case.
FIG. 5 shows an embodiment of a multiplexer in which the blocker
electrodes are part of a resonator structure R. The resonator
structure R can be acoustically active or inactive in this
case.
FIG. 6 shows an embodiment of a duplexer, wherein the blocker
electrodes of the blocker path BP are arranged in a resonator
structure R, which are interconnected in series to an inductive
element IE and not directly with the common terminal CC.
FIG. 7 shows an embodiment in which it is shown as an example on
the basis of a filter, which can be the transmit filter Tx or the
receive filter Rx, how doubled resonators represent a further
feature for reducing intermodulation products. The doubling can be
embodied in this case as a parallel doubling or as a serial
doubling.
In the case of parallel doubling, through contacts VIA can
interconnect lower and upper electrodes of doubled resonators.
Interconnected electrodes of doubled resonators are shown thicker
as examples in FIG. 7. Interconnected electrodes of doubled
resonators can be connected to one another via node points (NOD),
via which a mass terminal can also be produced, for example.
It is also possible that parallel doubled resonators are
additionally embodied as doubled in series.
FIG. 8 shows the equivalent circuit diagram ECD of an
electroacoustic resonator R. The equivalent circuit diagram
comprises in this case a static capacitance C.sub.0 and, connected
in parallel thereto, a series circuit made of a dynamic capacitance
C.sub.D and a dynamic inductance L.sub.D. At frequencies far away
from the acoustic operating frequency, the resonator is essentially
represented as a capacitive element having the static capacitance
C.sub.0. The dynamic capacitance C.sub.D and the dynamic inductance
L.sub.D are essentially negligible. It behaves differently in the
operating range of the resonator. The dynamic capacitance C.sub.D
and the dynamic inductance L.sub.D then essentially control the
behavior of the resonator, while the static capacitance C.sub.0
plays a subordinate role.
Depending on the dimensioning of the electroacoustic resonator R
and the definition of its operating range, a resonator may
therefore be operated as a solely capacitive element or as a solely
electroacoustic element or as a mixed form of both elements, so
that a resonator can be adapted to operate as a filter element in
the transmit filter or receive filter and simultaneously to
function as a blocker element in the blocker path. In this case,
essentially no other method steps are required for the production
to provide the resonator R in the blocker path, so that the
proposed multiplexer is producible without additional effort and
can be used with known methods for reducing intermodulation
effects.
FIG. 9 shows an embodiment of a multiplexer, wherein the blocker
path comprises a parallel branch resonator of the transmit filter
(Tx) or receive filter (Rx), in which the blocker electrodes CE are
arranged. Furthermore, the blocker path comprises an inductive
element IE, so that via the dimensioning of the electrodes CE and
the inductive element IE, a signal path can be obtained, via which
blocker signals can be intentionally diverted to ground.
FIG. 10 shows an embodiment of a multiplexer, in which the blocker
path BP comprises a series branch resonator having blocker
electrodes CE and a parallel branch resonator having blocker
electrodes CE2 and also an inductive element IE. The corresponding
electrode structures and the inductive element are selected
similarly to the embodiment of FIG. 9, so that good diversion of
blocker signals to ground is obtained.
FIG. 11 shows an embodiment of a multiplexer, in which the blocker
path BP comprises a first inductive element IE1, a second inductive
element IE2, and blocker electrodes, which are arranged in a
resonator, of a capacitive element CE. The values of the
inductances of the elements IE1 and IE2 and the value of the
capacitance of the capacitive element CE in the blocker path BP are
selected so that good diversion of blocker signals to ground is
obtained.
FIG. 12 shows an embodiment of a multiplexer, in which the blocker
path BP comprises a first inductive element IE1, a second inductive
element IE2, and blocker electrodes of a first capacitive element
CE1 in a first resonator and further blocker electrodes in a second
capacitive element CE2 in a parallel branch resonator. The values
of the inductances and capacitances of the corresponding inductive
and capacitive elements are selected accordingly to obtain good
diversion of blocker signals to ground.
FIG. 13 shows, similarly to FIG. 3, a front-end circuit, in which a
Tx filter was replaced by a band-stop NOT, which is
non-transmissive for frequencies of an Rx filter Rx2. As an
example, the critical case is shown in which transmit signals from
the band-stop NOT are mixed with blocker frequencies f.sub.blocker
at the common terminal CC and fall as interfering intermodulation
products in the filter Rx2. Intermodulation products can also
result which fall in another Rx filter. It also must be ensured
here using blocker paths at the node CC that the blocker
frequencies are eliminated.
It can thus be provided that, especially in receive paths for
navigation data to be received from satellites, reception can take
place undisturbed.
FIG. 14 schematically shows a mobile communication device having
diversity functionality. I.e., in addition to an antenna ANT, a
further antenna ANT2 exists, which fulfills additional transmit
and/or receive tasks. Each of the antennas can be interconnected
with a multiplexer MUL, MUL2. Blocker paths can now be provided in
each of the multiplexers MUL, MUL2, to eliminate intermodulation
products which can arise due to coupling of signals of one antenna
into the other antenna. It is also possible that one of the
multiplexers MUL, MUL2 comprises blocker paths to divert blocker
signals to ground, which would interfere with the reception in the
respective other multiplexer as intermodulation products.
FIG. 15 shows an embodiment of a multiplexer, wherein a stop
circuit made of an inductance L and an on-chip capacitance X is
interconnected between an antenna terminal ANT and the common
terminal CC. The on-chip capacitance can be a resonator in this
case or an on-chip element, which solely has a capacitive effect
and is constructed like a resonator. If the on-chip capacitance X
is a resonator, two stop frequencies thus exist, which are
generated by the stop circuit.
FIG. 16 shows a stop circuit between the common terminal CC and a
filter in the transmit path. The stop circuit can also be arranged
between the common terminal CC and a filter in the receive path.
The stop circuit comprises an inductance L and an on-chip
capacitance X. The on-chip capacitance X can again be a resonator
or a chip element solely having a capacitive effect (cf. FIG.
15).
A multiplexer according to the invention is not restricted to one
of the described exemplary embodiments. Combinations of the
exemplary embodiments and variations which comprise, for example,
still further inductive or capacitive elements in transmit filters,
receive filters, or further circuit elements, also represent
exemplary embodiments according to the invention.
LIST OF REFERENCE SIGNS
ANT, ANT2: antenna BAWR: BAW resonator BP: blocker path C0: static
capacitance CC: common terminal CC2: common terminal of the second
multiplexer CD: dynamic capacitance CE: capacitive element CE2:
further capacitive element CH: chip ECD: equivalent circuit diagram
EFI: electrode finger EL1, EL2: electrodes F.sub.blocker: blocker
frequency FRx2, FRx2, FRxn: receive frequencies FTx1, FTx2, FTxM:
transmit frequencies FTxm1: signal coupled from one antenna into
the other antenna, which is already an interfering intermodulation
product or results in an interfering intermodulation product in the
other antenna. GND: ground IDS: interdigital structure IE:
inductive element IE2: further, second inductive element LD:
dynamic inductance MN: adaptation network MUL, MUL2: multiplexer,
second, further multiplexer NOD: node point PL: dielectric layer R:
(electroacoustic) resonator Rx: receive filter Rx1, Rx2: receive
filter RxC, Rxn: receive terminal RxC1, RxC2, RxCn: receive
terminal SAWR: SAW resonator Tx: transmit filter Tx1, Tx2, Txm:
transmit filter TxC: transmit terminal TxC1, TxC2, TxCm: transmit
terminal VIA: through contact (via)
* * * * *